One method of treating respiratory distress and certain respiratory disorders (including Chronic Obstructive Pulmonary Disease or COPD and Obstructive Sleep Apnea or OSA) is the provision of Continuous Positive Airway Pressure (CPAP) or other forms of Positive Airway Pressure (PAP) to support a user's respiratory system. Non invasive respiratory pressurisation is commonly administered by delivering pressurised breathing gases to a user's mouth and/or nose.
PAP treatment is usually provided by a breathing assistance system. Breathing assistance systems generally incorporate a source of pressurised gases (potentially a compressor, pressurised gas canister or hospital compressed air supply) and an interface configured to deliver the pressurised gases to a user. Additionally, breathing assistance systems may incorporate a humidifier for heating and humidifying the breathing gases prior to delivery to the user.
Other supported breathing systems include ventilators and respirators. These may adjust pressure between inspiratory and expiratory phases of the breathing cycle, and typically include a return line from the interface.
Conventional interfaces are configured to form a seal with the user's face or upper airway to facilitate adequate pressurisation of the user's respiratory system. Forma™, Oracle™, Zest™ and Opus™ are examples of sealing respiratory user interfaces produced by Fisher & Paykel Healthcare. These interfaces are configured to seal with a user's face, mouth, nose and nares respectively.
The seal formed between the interface and user's respiratory system allows the mask pressure to be regulated by reducing gas leaks and providing a controlled breathing gases exhaust. Gases may be exhausted from the user interface directly to the surrounding atmosphere (through outlet vents) or to another component in the breathing assistance system responsible for controlling the exhaust of breathing gas.
Non-sealing interfaces, particularly nasal cannula, are often employed for supplemental oxygen therapy or other respiratory gases such as Heliox. Typical supplemental oxygen therapy interfaces deliver flow rates up to 5 l/min directly to the user's nares. Air from the user's surroundings is entrained with the oxygen during normal inhalation, the gases combining to deliver a gas mixture with elevated oxygen concentrations to the user's lungs.
Common supplemental oxygen therapy interfaces are supported by a pair of delivery lumen that loop over the user's ears. The lumen have small diameters (in the range 2-3 mm) and supply oxygen to both sides of the nasal cannula, providing essentially even flow to each nasal prong.
Facial masks are traditionally used for high flow oxygen therapy. Non-sealing high flow nasal cannula, such as Fisher & Paykel Healthcare's Optiflow™ Nasal Cannula, are also being promoted for flow rate based treatments (including high-flow oxygen therapy) where respiratory system pressure regulation is not a control objective.
Direct delivery of breathing gases to a user's nares can be advantageous as the gases can be administered at a greater temperature and humidity than is viable with facial masks.
In this specification, where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.